This invention relates to a magnetic disk device and, particularly, to a magnetic disk device for recording information relying upon a vertical magnetic recording system.
In a magnetic disk device employing the vertical magnetic recording system, when a magnetic field is applied from the outer side, the magnetic head works to concentrate the external magnetic field onto a main magnetic pole due to the constitution of the magnetic head often arising a problem in that the data recorded on a disk are destroyed. Since it is not possible to decrease the intensity of the external floating magnetic field itself acting on the magnetic disk device, it is necessary to provide the magnetic disk device with a function that exhibits shielding effect against the external magnetic field (to weaken the intensity of the external magnetic field).
Therefore, there has heretofore been devised a magnetic disk device as taught in JP-A-2003-77266 (patent document 1). The magnetic disk device of the patent document 1 comprises a rotary disk-type magnetic disk for recording information relying upon the vertical magnetic recording system, a magnetic head for recording information into the magnetic disk and for reproducing information from the magnetic disk, a disk drive mechanism for supporting the magnetic head in a manner to move in the radial direction of the magnetic disk, a housing having a base and a cover, and a shielding member constituted by using a magnetic member to magnetically shield the magnetic head.
In an embodiment illustrated in FIGS. 1 to 16 of the patent document 1, the housing accommodates therein the magnetic disk, magnetic head and disk drive mechanism, and a shielding member is provided over the upper surface, lower surface and side surfaces of the housing inclusive of the upper and lower sides over a range in which the magnetic head moves (prior art 1).
In an embodiment illustrated in FIG. 17 of the patent document 1, the housing accommodates therein the magnetic disk, the magnetic head, the disk drive mechanism and the shielding member, the shielding member being provided only over the base portion and the cover portion that are facing the magnetic head (prior art 2).
In an embodiment illustrated in FIG. 18 of the patent document 1, the housing accommodates therein the magnetic disk, the magnetic head and the disk drive mechanism, the housing is partly cut away, a shielding member is disposed therein, the front end side of the shielding member is extended to both sides of the magnetic disk, and the end surfaces thereof are faced to the end surface of the magnetic head (prior art 3).
In an embodiment illustrated in FIG. 19 of the patent document 1, the housing accommodates therein the magnetic disk, the magnetic head and the disk drive mechanism, a recessed portion is formed in the outer surface of the housing, a shielding member is disposed in the recessed portion, the front end side of the shielding member is extended to both sides of the magnetic disk, and the ends thereof are faced to the end of the magnetic head (prior art 4).